[hpsdr] 700MHz Full Power Bandwidth S/H

[Steve Bunch]

Maximo,

On Aug 30, 2010, at 4:22 AM, Maximo EA1DDO_HK1DX wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi,
> 
> Thanks Roland, Lester and Steve.
> 
> I understand the aliasing and undersampling method, but my question was about to sample higher frecuencies "directly", not with undersampling.
> 
> So,
>  
> .- "700 MHz Full Power Bandwith S/H", is always talking about undersampling.
> 
> .- We can not set the LTC2208 to sample 60 MHz anywhere (between 0,1 to 700 MHz), for example, We can not sample from 100 to 160 MHz directly, without undersampling.
> 
> .- LTC2208 has always to sample from 0,1 to 61 MHz.
> 
> Are that sentences correct?

Yes.

The bandwidth of the Sample/Hold circuitry refers to its ability to take a "snapshot" of the incoming signal and hold it long enough for the Analog-Digital conversion to take place.  The snapshot still takes finite time, during which a change will occur in the signal, so the sample will become increasingly inaccurate as you go up in frequency.  This is why the quality of the sampled signal will go down as you go up in the Nyquist zones.  The A/D conversion rate has a lower maximum because it's harder to do a fast A/D than a fast sample/hold.

73,
Steve, K9SRB

> Thank you very much.
> 
> 73, Maximo - EA1DDO
> 
> 
> 
> 
> 
> 
> 
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